1. Field of the Invention
This invention relates generally to internal combustion engines. More particularly, the invention relates to an internal combustion engine of the type wherein an engine body itself is rotated to drive an output shaft.
2. Description of the Prior Art
As is well known, most of the conventional internal combustion engines equally incorporate a crank mechanism for converting piston reciprocation into rotation of the output shaft. Such a crank mechanism has been found to result in a non-negligible energy loss.
In view of the above problem, Japanese Patent Publication No. 2-31761 (Published: Jul. 16, 1990; Laid-open: Jun. 11, 1983), which was filed by one of the inventors of the present invention, discloses an internal combustion engine in which a pair of pistons are made to rotate with a cylindrical engine body as the pistons reciprocate in response to explosive combustion occurring in a combustion chamber between the pistons. The rotation of the engine body is directly transmitted to an output shaft without requiring a crank mechanism.
Specifically, the engine body disclosed in the above Japanese patent publication is rotatably received in a pair of cam cylinders, and has two pairs of longitudinal guide slots. The respective pistons have guide projections slidably guided by the longitudinal guide slots of the engine body, so that the pistons are rotatable with but slidably reciprocatable relative to the engine body. Each cam cylinder is internally formed with a curved cam groove, whereas each piston carries a pair of piston pins penetrating through the longitudinal guide slots to fit into the cam groove. The cam groove have such a profile that the piston makes one full rotation with the engine body as the piston makes two reciprocations.
Obviously, the engine described above requires no crank mechanism, and therefore has an advantage of being higher in energy efficiency than the conventional reciprocating engines. Further, the rotation of the engine body causes air within the combustion chamber to rotate, so that the air can be forcibly and uniformly mixed with the fuel to provide an enhanced combustion efficiency.
A similar internal combustion engine is also disclosed in Japanese Patent Publication No. 2-35841 (Published: Aug. 14, 1990; Laid-open: Jul. 21, 1983) which was also filed by one of the inventors of the present invention.
According to either of the two Japanese patent publications, a chamber lid is attached to each end of the engine body to define an air supply chamber extending into the hollow interior space of the corresponding piston from the side thereof axially away from the combustion chamber. The air supply chamber is compressed when the piston moves toward the chamber lid, namely toward the lower deadpoint. The air thus compressed within the air supply chamber is introduced into the combustion chamber for scavenging and for performing air supply for combustion.
Obviously, it is preferable that the air supply chamber is compressed to a high extent for effectively scavenging the combustion chamber and for increasing the combustion efficiency. However, the chamber lid of the prior art is not fully insertable into the piston at the lower deadpoint thereof, so that the air supply chamber is compressed only to a limited degree.